This year's most interesting Billboard successes have been staged by one very unlikely hit machine – the scrappy independent scene, once the province of self-professed rock geeks.

In recent weeks, albums from indie acts The Shins and Arcade Fire both recently debuted at No. 2 on the Billboard charts, selling about 90,000 units each. The two bands soared past releases by entrenched mainstream artists such as Christina Aguilera and Nickelback. And this week, Modest Mouse, a longtime independent powerhouse – now signed to Sony – made a splash with "We Were Dead Before the Ship Even Sank."

The commercial explosion is no accident. Indie labels may have finally found a way to harness the Internet's sizable community of tastemakers. These music labels are bringing bloggers who have a reputation for posting legal and illegal MP3 tracks into the fold by purposefully leaking albums ahead of the release.

Much as iTunes created a palatable model of digital downloading, these labels increasingly rely on carefully controlled – and sometimes uncontrolled – leaks of MP3 files to publicize upcoming records. Ever since the arrival of file-sharing sites such as Napster and Grokster, entertainment firms have grappled with the question of whether to crack down on the sharing of copyright material or find a way to harness its spread to boost music sales. Even as major entertainment firms mull similar questions relating to the spread of unauthorized clips on YouTube, the popular video-sharing site, they will be keeping close watch on the effectiveness of such "leak" strategies by small labels.

"We'll release an MP3 early into a campaign," says Sonya Kolowrat, a publicist at The Beggars Group, an indie label that's home to the Pixies and Blonde Redhead. The label will post tracks on a special page of its website and give music bloggers individual codes to access the page.

So far, bloggers have been willing to cooperate with labels in exchange for access to songs. "A lot of the labels have been easy to work with and have been very transparent about what they want," says David Greenwald, who posts tracks from coming indie albums on his blog The Rawking Refuses to Stop. "If the label says, 'We don't want you to leak this record,' that's not something I'm going to do," he adds.

The system that has developed strongly resembles the current rapport between radio stations and record labels – the blogs, like radio stations, receive early access to promotional singles as long as they agree not to play the entire album. Because most commercial radio stays away from rough-around-the-edges indie rock, the blogs may be the only outlets available.

The promotions firm Cornerstone, with clients such as Gnarls Barkley and Lily Allen, has an entire department devoted to working with music bloggers and Internet tastemakers. According to copresident Jon Cohen, the firm identifies an artist's existing fans among music bloggers and "empowers" them, as he puts it, by providing them with audio and video content, or tickets and prizes for contests. The firm tracks over 1,600 blogs.

Major labels frequently "watermark" promotional CDs sent to reviewers with a digital signature traceable to the recipient in case of an unauthorized leak. But some smaller labels may even be taking the next step and leaking entire albums themselves.

Kris Gillespie, who manages Domino Records, says leaking wasn't out of the question for his label, the home of the rockers Franz Ferdinand and indie buzzmakers the Arctic Monkeys.

"We were seriously considering leaking tracks," Gillespie says of the latest Franz Ferdinand album, "because the watermarks and copy protection were almost doing too good a job."

Gillespie says he checks peer-to-peer trading sites every day to see if the new Arctic Monkeys album has leaked, "but more out of curiosity than out of vigilance," he notes.

With the formation of this new Internet-industrial complex, the absence of music trading can signal serious problems. "If no one's bothered leaking the album the week before the release date, the fear would be that no one cares," says Brendan Bourke, of the music publicity firm TagTeam. "When you're getting within a few weeks of a release, you want people to start talking about it. It almost behooves you to leak."

The multimillion dollar question, of course, is whether leaks and free singles, for all their publicity payoff, can later hurt an artist's sales. No one can say for sure, but there is one point where the blogger, industry executive, and PR guru agree: In the recording industry, there may well be such a thing as bad publicity.

"A leak is only going to hurt album sales if the album itself is bad," says blogger Greenwald. For the major record labels, who are invested heavily in retail, he notes, the fear is that no one will buy the album. "That happens," he says, "because a lot of the bands are not very good."